Overload and reverse current relay.



F. CONRAD.

OVERLOAD AND REVERSE CURRENT RELAY. APPLICATION FILED MAY 22, 1909.

1,137,840. Patented May 4;, 191-5.

2 SHEETSSHEET l- WITNESSES: INVENTUR v ATTORNEY F. CONRAD.

OVERLOADAND REVERSE CURRENT RELAY.- APPUCAHON FILED MAY 22, 1909.

1 ,137,840. Paiented May 4, 1915.

2 SHEETS-SHEET 2.

WITNESSES: l

T ATTORNEY m nes FRANK GQNRAD, F S'WISSVALE, PENNSYLVANEA, ASSIGNQR TO WESTINGHOUSE ELECTBQXC AND MANUFACTURING COMPANY, A GOEPQEATION 03F PENNSYL- VAMA.

OVERLOAD AND REVERSE CURRENT RELAY,

instead Application filed IEay 22, 1909.

To all whom it may concern:

Be it known that I, FRANK CONRAD, a citizen of the United States, and a resident of Swissvale, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Overload and Reverse Current Relays, of which the following is a specification.

My invention relates to relay devices, and

particularly-to such devices as are adapted to protect electrical circuits from 11'1]1II16S resulting from overloads or from reversals of the direction of current flow therein.

The object ofmy invention is to so construct and arrange the parts of an instrumerit of the character indicated that the movable member thereof may be caused to move at a substantially uniform rate when the initial actuating force exceedsia predeaoftermined value and during the continuance of the abnormal circuit conditions.

Figure 1, of the accompanying drawings is a View, in side elevation and in section. of an instrument embodying the invention.- Fig. 2 is a plan view of the instrument of Fig. 1, some of the parts being shown in section for the sake of clearness of illustration, and Fig. 3 is a diagrammatic view illustrating the circuit connections of the in- .30 strumen't.

Secured, by means of screws 1, to the main frame 2 of the device, is a two-part laminated magnetizable core 3-4, the part 3 of which is of U-shape and is provided with a winding 5 the respective terminals of which are connected to conductors 6 and 7 of the circuit to be protected. lhe part 4 comprises two alined polar projections 8 and 9 having opposing faces and a main polar pro- 4.0 jection 10 which difi'ers in polarity therefrom and extends between and somewhat beyond the said opposing faces, from which it is separated by suitable air gaps. The

main polar projection 10 is surrounded by i a coil 11 that is connected in series with one of the conductors of the circuit 6-7, or is otherwise arranged so as tobe supplied with current which, is proportional, in amount, to that traversing the said circuit,

.59 and also by a coil 11 that is connected between the terminals cf the winding 5 on the core part 3, so that the currents induced therein may be supplied to the said-winding. Mounted upon a shaft 1.2 having, at its 5:3 ends, bearings 13 and lethat ere support- Specification of Letters Patent.

Patented May at, 1.9115,

Serial No. 497,799.

ed by the frame 2, and arranged to rotate between the opposing faces of the polar projections of the core 34, and also between the polar faces of permanent magnets 15, by which its movements are retarded, is a conducting disk 16 the movements of which and of the shaft 12 are opposed by a spiral spring 17 the inner end of which is secured to a hub on the shaft 12. The outer end of the spring 17 is secured to a downwardly extending projection 18 carried by an arm 19 the inner end of which is secured to a bushing 20 that surrounds, the upper end of the shaft 12 and is rotatable within a supporting block or member 91 therefor that is secured to the frame 2.

. Secured upon the upper end. of the bushing 20', and located within a recess in the upper face of the member 21, isa spring washer" 22 that serves to .introducea suflicient degree of friction between the rela-;

tively mpvable parts to retain the arm 19 in any position to which it may be adjusted, ir-.

respective of the torque exerted by the spring 17, the spring washer 22 being secured in position by means of another washer 23 and an upset portion of the bushing 20.

The arm 19 is provided, at its outer free end, with a downwardly extending index portion 24 that coijperates with a cylindrically curved scale 25 the divisions of which represent suitable units, such as current values, the arrangement being such that when the index 24 occupies a position opposite the zero point of the scale the spring 17 opposes no force to the initial movement of the shaft 12 and the disk 16. A handle26 is provided for operating the movable arm 19 to adjust the torque exerted by the spring upon the shaft 12.

The shaft 12 carries a movable contact 1 be intained in engagementiwith a stop 11o 31 which is carried by an arm 32 that is mounted similarly to the arm 19 and is provided with an operating handle 33 and an index portion 34: that also cooperates with the scale 25.

It will be understood that the period during which abnormal circuit conditions will exist in the circuit 67, before engagement of the contact terminals 27 and 28 occurs, will depend upon the distance between the said terminals, the positions of the stop 31 and the arm 32 determining the said distanee. In order to prevent movement of the arm 31, in a clockwise direction, beyond the position of the arm 19, the projection 18 is extended into the path of movement of the stop 31.

While the specific form of the device herein set forth is different from that set forth in applicants co-pending application Serial No. 259,388, filed May 8, 1905, the arrangement of the core parts and of the winding and their connections is such as to insure a similar mode of operation and an equivalent result.

The current traversing the winding 11 produces a flux in the polar projection 10 of the core, which, in turn, induces, in the coil 11, a current that is supplied to the winding 5 upon the core part 3. These currents in the windings 5 and 11 cause a torque to be exerted upon the disk 16 that is propor tional to the square of the current traversing the coil 11, as well as that traversing the circuit 6-7, this being an ammeter torque. The winding 5, being alsoconnected between conductors 6 and 7, is traversed by a current that is proportional to the electromotive-force of the said circuit, with the result that another torque is exerted upon the disk 16 that is proportional to the product of the current, voltage and power factor of the circuit 67, this being a wattm'eter torque. The arrangement is such that the ammeter and wattmeter torques oppose each other, and also such that the ammeter torque acts in opposition to that of the spring 17. If the a'mmeter torque becomes sufiicient to overcome that exerted by the spring 17, a rotative movement of the shaft 12 and of the contact terminal 27 will occur, with the re sult that the switch member 27 will be finally brought into engagement with the stationary contact terminal 28, thereby establishing the circuit of the tripping magnet 29 of the circuit-breaker and causing interruption of the circuit 6-7.

It will be understood that the above-specified condition will occur when a current amounting to an overload traverses the ci'rcuit 6-7. The degree of overload that will cause tripping of the circuit-breakers de pends upon the position of the arm 19, which may be adjusted, and of the consequent degree of torque exerted upon the shaft 12 by the spring 17 The period during which the overload must cont nue n order to cau se interruption of the circuit is dependent upon the position of the arm31, and the consequent distance between the switch contacts 27 and 28. If, for any reason, the current in the circuit 6-7 becomes reversed in direction, the wattmeter torque will become reversed and will then assist or supplement the ammcter torque, the algebraic sum of which will be exerted upon the .disk 16 to cause rotative movement thereof and engagement of the switch contacts 27 and 28, provided the said abnormal condition continues for a sufficient period of time. In order that, with a given amount of over load upon the circuit 67, or with a given value of current traversing the same in the reverse of normal direction, the disk 16 and shaft 12 may be caused to rotate at a uniform speed and may continue to rotate until contact terminals 27 and 28 are caused to engage, irrespective of theincreasing torque exerted by the spring 17, the disk 16 is pro vidcdwith a spiral contour and is so arranged that an increasing area thereof is presented adjacent the polar faces of the core parts 8 and 4 as it is rotated from its initial toward its final pesition, the torque exerted eleetromagnetically upon the disk being thereby caused to increase at substantially the same rate as the torque exerted by the spring 17 increases.

The present arrangement differs from that heretofore commonly employed in measuring instruments of the indicating type in that the disk will be caused to move at a uniform rate from its initial to its final position when the instrument windings are traversed by constant amounts of current, whereas, in previously constructed instruments, the deflection of the disk has been in proportion to the square of the amount of current traversing theinstrument winding, and the rate of movement of the disk is not uniform. By reason of the uniformity of the rate of movement of the disk, the time required for the disk to move from any predetermined initial position to its final position, may be accurately determined and the scale of the instrument may be calibrated with divisions of equal length corresponding to suitable periods of time. p I claim as my invention:

1. A relay instrument comprising a magnet, a disk having a spiral contour and mounted for rotative movement to present an increasing area adjacent a polar face of the magnet as it moves from its initial posi-' tion, and an opposing spring the torque of which varies at substantially the same rate as the electromagnetic torque which it op'- poses. i 2. A relay instrument comprising a magnet, a disk having a spiral contour and mounted for rotative movement to present a portion of increasing radius adjacent a polar face of the magnet as it moves from its initial position, and means for restraining the disk and holding it in'its initial positon until a predetermined opposing value of magnetizing current is reached, and then further progressively increasing the restraining force on the disk in proportion to the increase in the opposing torque caused by the rotation of the spiral disk.

3. A relay instrument comprising a magnet, a disk having a spiral contour and .mounted for rotative movement to present 4. A relay instrument comprising a magnet, a disk having a spiral contour and mounted for rotative movement to present an increasing area adjacent a polar face of the magnet as it is rotated from a predetermined position, and a resilient means for exerting an opposing torque that varies as the electromagnetic torque exerted upon the disk Varies.

5. A relay instrument comprising a magnet, a disk having a spiral contour and mounted for rotative movement, and a resilient means for opposing movement of the disk, the disk radii being of such progressively greater lengths that the electro-magnetic' torque exerted upon the disk will increase at substantially the same rate as that exerted by the said resilient opposing means.

In testimony whereof, I have hereunto subscribed my name this 19th day of May, 1909.

FRANK CONRAD. Witnesses:

O. AOLBARY, B. B. Hmns.

Gupta! of this patent maybe obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. 0. 

